1882 .] 
467 
[Merrill. 
I think that the slide undoubtedly corresponds to the hand spec- 
imen now bearing the collection number 20,506. Opposite this 
collection number, in a catalogue, is the old collection number 
2614. 
Concerning the Prussian blue grains noticed by Zirkel in Nos. 
300, 301 (Trachytes) and 613 (Basalt) I am prepared to express 
an opinion only concerning No. 613. I think Mr. Wadsworth is 
correct in regarding the blue grains in this section as some impur- 
ity, foreign to the rock. 1 I think that they are not in the rock 
section : they are not confined to the feldspars, but also appear 
in (or rather on) the augites. I also found some of these blue 
grains lying outside the section, in the balsam. The grains are 
curiously evenly distributed throughout the section and, were it 
not for those lying outside the section in the balsam, might well 
be thought to belong to the rock, since in some cases they seem to 
have been deposited in little hollows in the uneven surface of 
the section, and, even by careful focusing, then appear as if in 
the rock. In recently prepared sections from basalts of the 
same region no such blue grains were found by me. We should 
remember that Professor Zirkel in his Report, p. 251 did not call 
these grains Hauyne but alluded to them as being of “ an unknown 
nature (possibly Hauyne.)” 
Concerning No. 464 called by Zirkel a rhyolite, and No. 303 
called by him a beautiful trachyte, I agree with Mr. Wadsworth 2 
in considering them quite or nearly identical with each other. 
Mr. Wadsworth 3 thinks that in the same series with these two 
rocks belong Zirkel’s granite-porphyries Nos. 120 and 133. With 
this view I do not agree. These numbers (120 and 133) appear 
to me to be ante-Tertiary rocks, the quartzes carrying no glass, 
but liquid, inclusions (120), and there are characteristic titanites 
in No. 133. Titanite occurs in not a few trachytes, but rarely in 
rhyolites, as an accessory ingredient. They also contain apatite 
which, in No. 133, is in thick sections and in No. 120 is mostly 
contained within the fragments of mica. Numbers 464 and 303 
show fine glass inclusions in their quartzes, and I did not notice 
titanite or apatite. 
1 These Proceedings, Vol. xxi, p. 267. 
2 These Proceedings, Vol. xxi, p, 268. 
s Ibid. 
